Currently, the anode casting process is based on casting molten cooper on a mould (usually made of copper) which contains the cavity in the shape of the desired anode.
Once the copper has been cast, it goes through a process of rapid cooling by means of sprinklers, and an ejector in the shape of a rod or steel cylinder which ejects the anode that has already been solidified.
In general, moulds are mounted on a rotating carousel or “casting wheel” in such a way that the rotating thereof allows for the continuous process of casting, cooling and ejecting the anodes.
Each mould when finishing one turn of the wheel is again filled with cooper and so on.
In order for the liquid cooper not to get adhered to the mould and can be ejected by the rod, it is necessary to add a layer of the release dusting agent material which acts as an isolation material and prevents the liquid copper from being adhered to the solid copper of the mould.
The worldwide used material is a derivative from calcium powder or barite powder which are mixed with water and sprayed by sprinklers on the inner faces of the mould.
As they are non-water soluble materials, the solution must be permanently agitated so as the powder is not precipitated.
When being applied with sprinklers it is decanted by gravity on the mould in a way that mostly covers the lower zones thus generating a thinner layer with reduced coverage on the vertical side faces of the mould.
This method of adding a release dusting agent is practically used worldwide on every casting wheel in the manufacture of copper anodes, however this has a big disadvantage which is that the water reacts in a explosive way when in contact with the liquid copper and therefore the application of the release dusting agent on the aqueous solution must be done before the liquid copper is poured by the ladles and it should be guaranteed that the mould is hot enough so as it evaporates a 100% of the water applied with the release agent, on the contrary, any drop will cause a chemical explosive reaction which can leave a crater on the anode, which will cause its immediate rejection or in the worst case scenario could cause such a big explosion which can result in damaging both equipment and the personnel in charge of them, both types of situations have happened and been registered.
Another present problem is that the mouths of ladles which cast the liquid copper must be cleaned in-between castings in order to prevent the copper from solidifying and subsequently that the mouths are closed, which are an obstacle for the right casting and even distribution of the molten inside the mould which is absolutely necessary for the right shape for the anode.
In turn, if the mouths of ladles are closed by accumulation of solidified copper, it occurs a phenomenon in which the cast copper falls in the shape of jets and not with the shape of cascade as normally occurs.
This jet concentrates all of the copper casting in one single point, thereby displacing the release agent applied to the mould, thus causing the anode to adhere to the mould, which implies that both the anode and the mould must be discarded and removed from the casting wheel which results in halting the production process.
In order to avoid this situation, an operator must be permanently exposed to the heat and liquid cooper so as to manually throw powder release agent on the mouths of ladles.
As the ladles contain liquid copper, it is not feasible to apply a coverage by means of sprinklers considering the explosion that would take place, therefore the operator is obligated to perform the manual constant application in big quantities of said agent, since the powder does not have adhesion capacity by itself and it is not adhered to the ladle, being rapidly displaced in each copper casting on the mould.
There are some release agents having an electrostatic principle in the state of the art.
For example, document CA 2345922 discloses a method for coating an extrusion plate which is at 450° C. by means of a BN powder as a separating agent which is adhered to the plate by means of an electrostatic charge.
Document GB 1288292 discloses a method for coating a mould surface of a ingot by means of spraying said coating from a nozzle against the mould surface to be coated wherein said coating contains an organic liquid suspension of granular materials which comprise 85% to 96% in weight of a refractory material and 4% to 15% in weight of an organic powder material.
The coating is applied on the mould surface by means of electrostatic charges.
Document JPS 58192657 discloses a method for coating a material of a casting mould by means of suction which attracts the material dust of the mould coating material and that is electrostatically applied with positive charge on the surface of molten iron which consists of an iron sand layer having negative charge.
Document JPS 61199543 discloses a method for improving the quality of a product by means of the utilization of a painting containing electrostatically refractory particles with respect to a part of the mould shielding and the coating of a fixing agent to said element thereby forming a material layer for coating the mould.
Document KR 20090082106 discloses an oil type release agent for metal casting characterized in that contains 0-7.5% by mass of water consisting of one or two kinds of water selected from distilled water, ion-exchange kinds of water, tap water and water includes any one of aforementioned kinds of water and electrolyte(s) dissolved in any one of aforementioned kinds of water, and 0.3-30% by mass of a solubilizing agent.
Also, it discloses a spray method using this oil type release agent, and an electrostatic spray apparatus for this oil type release agent for a mould.
U.S. Pat. No. 5,437,326 discloses the Electrostatic application of a dusting of dry, electrostatically adherable, thermally insulative powder particles over a workface of a continuous metal-casting machine in which the mould surface or surfaces which provide the workface or workfaces revolve in a generally oval course.
A dry dusting of protective powdery refractory material is applied to the workface after being entrained in an air stream and electrostatically charged by suitable electrostatic apparatus.
The workface to be dusted is electrically grounded for attracting the charged powder particles for adhering them to the workface.
The resultant coating formed by the dusting so deposited is remarkably uniform over a substantial area of the workface, a phenomenon explainable by mutual electrostatic repulsion of the dry powder particles being deposited.
In this method continuously re-applied dusting over the workface during a continuous cast provides an immediately useful repair or replacement of dusting powder lost from the coating on the workface of a revolving mould surface during casting. The dusting may be continuously removed.
The dusting may be removed at will by means of air.
None of the aforementioned documents approaches the technical problems in order to prevent copper from being adhered to the edge of the ladle and also to prevent the ejector rod located below the copper anode mould from being adhered therein due to the molten copper gets adhered between the rod and the mould as the molten coppers gets cold.
The present invention solves these problems by using a device which spray dry dusting through an air jet wherein it goes through a nozzle which charges the particles with high voltage and negative charge.
In turn, the metallic pieces being part of the ladles are connected to ground (positive charge) with which the sprayed particles are attracted and adhered to the ladle surface as well as to the metallic surfaces by the difference of charges.
In this way, it is not necessary to use water as a conductive means of the release agent and it can be directly sprayed on the ladles containing liquid copper.
In addition, the invention can be implemented as a manual tool keeping the operator away from the direct contact with copper or else can be mounted on a robotic arm with a sliding rails system in such a way the process can be made automated.
Another advantage of this invention is that the same robotic arm, sliding rails or manual tool can spray the release agent directly on the mould in which the copper would be poured, in this way the installation of the automated station injecting the release liquid agent which is currently used, is avoided.
On the other hand, this invention allows accelerating the anode moulding process since it is not necessary to wait for the release liquid agent to evaporate all the water in order to avoid an explosive reaction with the liquid copper.
Also, it mean an increase of safety, when eliminating the water in contact with the liquid copper during the moulding process.
Another advantage of this invention is that when using dry dusting being adhered to the surfaces with opposite charge, no displacement of the liquid release agent occurs, therefore the application will be uniform on the cavities and vertical walls of the mould as well as on the ladle.
Also, the electrostatically charged dust tends to accumulate thus achieving a much higher thickness of the decanted material in comparison to the one achieved with the application based on water.
Finally since there is no evaporation nor ebullition, the layer of the electrostatically applied release agent to the mould is very uniform and smooth, thereby improving the surface quality of the cast anode.
Due to the aforementioned, an objective of the present invention is the addition of a dusting release agent to be electrostatically adhered to the edge (lip) of the ladle in order to prevent the molten liquid copper from being adhered to said ladle.
Another objective of the present invention is adding a dusting release agent which can be electrostatically adhered to the anode mould and particularly to the ejector rod to prevent said rod from being adhered therein thereby facilitating the ejection of the anode from the mould.